1. CHEMISTRY MS. MATTSON STOICHIOMETRY

2. Stoichiometry the mole-mass relationship between reactants and products. Molecular Mass measured in atomic mass units (a.m.u.) Review: Calculate the molecular mass of chloroethane C 2 H 5 Cl. 64.5 a.m.u.

3. STOICHIOMETRY Mole A unit that refers to the number of molecules or ions that take part in a chemical reaction. Molar Mass One mole is equal to the molecular mass in grams. Ex: C 2 H 5 Cl = 64.5 a.m.u. = 1 mole = 64.5 grams Potassium (K) has molecular mass 39.1 a.m.u. What is 1 mole of potassium in grams? 39.1 grams

4. STOICHIOMETRY Molecular Mass (a.m.u.) = Molar Mass (g) = 1 mole Activity 1 Given molecule A in grams show the equation that would convert grams of A to moles of A. Given the moles of molecule B show the equation that would convert moles of B to grams of B.

5. STOICHIOMETRY Problem 1 Convert 15.0 grams of C 2 H 4 to moles of C 2 H 4. 0.536 moles Convert 0.536 moles of HCl to grams of HCl. 19.6 grams

6. STOICHIOMETRY Molecular Mass (a.m.u.) = Molar Mass (g) = 1 mole Activity 2 Given the reaction 2A + 3B  A2B + B2 show the equation that would convert the grams of A into the grams of B that are required to fulfill the reaction. Grams to moles to moles to grams!

7. Problem 2 Sodium hypochlorite (NaOCl) is best known as household bleach. It is prepared by reacting sodium hydroxide (NaOH) with chlorine Cl 2 : 2NaOH + Cl 2  NaOCl + NaCl + H 2 O How many grams of NaOH are needed to react with 25.0 g of Cl 2 ? 28.2 g NaOH STOICHIOMETRY

8. Problem 3 Aspirin is prepared by a reaction of salicylic acid (C 7 H 6 O 3 ) with acetic anhydride (C 4 H 6 O 3 ) according to the following equation: C 7 H 6 O 3 + C 4 H 6 O 3  C 9 H 8 O 4 + CH 3 COOH Salicylic acid Acetic anhydride Aspirin 138.1 g 102.1 g 180.2 g How many grams of acetic anhydride are needed to react with 4.50 g of salicylic acid? 3.33 g C 7 H 6 O 3 How many grams of aspirin will result? 5.87 g C 9 H 8 O 4 STOICHIOMETRY

9. Problem 4 In preparation of iron from hematite Fe 2 O 3 reacts with carbon: Fe 2 O 3 + C  Fe + CO 2 How many grams of carbon are needed to react with 525 g of hematite? 59.2 g C

10. STOICHIOMETRY Problem 5 Magnesium metal burns in oxygen to form magnesium oxide, MgO2. Write and balance an equation for this reaction. 2Mg + O 2  2MgO 2 How many grams of Mg(MM 24.3g) are needed to react with 25.0 g of O 2 (MM 32.0g)? 38.0g Mg How many grams of MgO 2 (MM 40.3) will result? 63.0 g MgO 2 How many grams of O 2 are needed to react with 25.0 g of Mg? 16.5 g O 2 How many grams of MgO 2 will result? 41.5 g MgO 2